1. Field of the Invention
The present invention relates to a method of driving a display device and to a display device using the driving method. In particular, the present invention relates to a method of driving an active matrix semiconductor display device having a thin film transistor (hereafter referred to as a TFT) manufactured on an insulating surface. Further, the present invention relates to an active matrix semiconductor display device using the driving method, and among active matrix semiconductor display devices, in particular relates to an active matrix liquid crystal display device. Furthermore, the present invention can also be applied to passive matrix semiconductor display devices.
2. Description of the Related Art
Techniques of manufacturing a TFT by forming a semiconductor thin film on a low cost glass substrate have rapidly developed in recent years. The reason for this is that the demand for active matrix semiconductor display devices (liquid crystal panel) has increased.
An active matrix semiconductor display device is a device in which a pixel TFT is placed in each of several hundreds of thousands to several millions of pixels arranged in a matrix state (this circuit is referred to as an active matrix circuit), and in which an electric charge delivered to a pixel electrode in each pixel is controlled by a switching function of the pixel TFT.
A TFT using amorphous silicon formed on a glass substrate is used in a conventional active matrix circuit.
Using a quartz substrate, active matrix semiconductor display devices having a TFT using a polycrystalline silicon film formed on the quartz substrate have recently been realized. Peripheral driver circuit for driving the pixel TFTs can also be manufactured on the same substrate as the active matrix circuit in this case.
Furthermore, techniques of manufacturing a TFT in which a polycrystalline silicon film is formed on a glass substrate by utilizing a technique such as laser annealing are also known. The active matrix circuit and the peripheral circuits can be integrated on the same glass substrate if this technique is utilized.
The active matrix semiconductor display device is often used recently as a display device for a personal computer. Further, large screen size active matrix semiconductor display devices have come to be used not only in notebook type personal computers, but also in desktop type personal computers. Further, projector devices having small size and using a small size active matrix semiconductor display device having high definition, high resolution, high quality have been basking in the spotlight. Among these, high vision projector devices capable of displaying a very high resolution image have been focused upon.
Using an active matrix semiconductor display device or a passive matrix semiconductor display device corresponding to high resolution to display a conventional image signal corresponding to low resolution (hereafter referred to as a video signal), it is necessary to write the video signal into memory one time and then to convert the format, and it is necessary to incorporate memory and circuits for controlling the memory outside of the active matrix semiconductor display device. Furthermore, a video signal corresponding to low resolution which has been converted in format so as to correspond to high resolution has a problem in that dots in an outline portion become easily noticeable because the dots are enlarged.